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Definition
of Glaucoma |
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Glaucoma
is a group of eye diseases that damages the optic
nerve which connects the eye to the
brain. The optic nerve is the main carrier of
vision information to the brain. The optic nerve
is made up of a huge number of nerve fibers, like
an electric cable containing a huge number of
wires. Glaucoma can damage these nerve fibers,
causing blind spots to develop. When sufficient
fibers have been lost or damaged, vision may be
affected, first by loss of side vision and then
later the loss of fine vision in the center. Usually
people don't notice these blind areas until much
optic nerve damage has already occurred. Blindness
results if the entire nerve is destroyed.
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Eye |
Glaucoma
Suspect |
Advanced
Glaucoma |
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Cause
of Glaucoma |
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Clear
fluid, called the aqueous humor, circulates inside
the front portion of the eye. A small amount of
this fluid is produced constantly, and an equal
amount flows out of the eye through a microscopic
drainage system, maintaining a constant level
of pressure within the eye. Because the eye is
a closed structure, if the drainage area for the
aqueous humor (the drainage angle) is blocked,
the excess fluid cannot flow out of the eye. Fluid
pressure within the eye will increase, pushing
against the optic nerve and potentially causing
damage.
In some people, the damage to the optic nerve
is caused by raised pressure. Others may have
an eye pressure within normal limits but damage
occurs because there is a weakness in the optic
nerve. Glaucoma results when pressure inside the
eye is more than what the optic nerve can withstand.
This pressure, if left untreated, can permanently
damage the optic nerve causing progressively serious
vision impairment.
The exact cause of glaucoma is not known, but
if detected at an early stage and treated promptly,
glaucoma can usually be controlled with little
or no further vision loss. Regular eye exams offer
the best chance for early diagnosis, as there
are no symptoms of glaucoma until the disease
is well advanced and irreversible damage has occurred.
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Different
Types of Glaucoma |
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There are four
main types:
1.
Chronic Open-angle Glaucoma:
This is the most common
form of glaucoma in the United States. The drainage
angle of the eye becomes less efficient over time,
and pressure within the eye gradually increases,
which can damage the optic nerve. In some patients,
the optic nerve becomes sensitive to normal eye
pressure and is at risk for damage. Treatment is
necessary to prevent further vision loss. Chronic
open-angle glaucoma damages vision so gradually
and painlessly that you are not aware of trouble
until the optic nerve is already injured.
2. Angle-closure Glaucoma:
Sometimes the drainage
angle of the eye may become completely blocked.
In the eye, the iris may drop over and completely
close off the drainage angle. You can imagine this
occurring much like a sheet of paper floating over
a drain. If the paper suddenly drops over the opening,
the flow is abruptly blocked. When eye pressure
builds up suddenly, an acute angle-closure glaucoma
attack occurs. Symptoms may include:
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Blurred vision |
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Severe eye pain |
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Headache |
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Rainbow-colored halos around
lights |
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Nausea and vomiting |
This is a true emergency.
If you have any of these symptoms, call your ophthalmologist
immediately. Unless this type of glaucoma is treated
quickly, blindness can result. In some patients,
glaucoma has features of both the chronic open-angle
type and the acute angle-closure type. This may
be called chronic angle-closure glaucoma or mixed
mechanism glaucoma.
3. Secondary Glaucoma:
They develop as a complication of other
medical conditions. They are sometimes associated
with eye surgery or advanced cataracts,
eye injuries, certain eye tumors, or uveitis
(eye inflammation). One type, known as pigmentary glaucoma,
occurs when pigment from the iris flakes off and
blocks the meshwork, slowing fluid drainage. A
severe form, called neovascular glaucoma,
is linked to diabetes. Also, corticosteroid drugs
used to treat eye inflammations and other diseases
can trigger glaucoma in a few people. Treatment
is with medicines, laser surgery, or conventional
surgery.
4. Developmental / Congenital
Glaucoma: Some children are born with defects
in the angle of the eye that slow the normal drainage
of fluid. Children with this problem usually have
obvious symptoms such as big, cloudy eyes, sensitivity
to light, and excessive tearing. Surgery is usually
the suggested treatment, because medicines may
have unknown effects in infants and be difficult
to give to them. The surgery is safe and effective.
If surgery is done promptly, these children usually
have an excellent chance of having good vision.
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Incidence
of Glaucoma |
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Some
form of glaucoma affects about 2 in 100 people
over the age of 40. Open-angle glaucoma, the most
common form of glaucoma, affects about 3 million
Americans, half of whom don't know they have it.
Glaucoma is the second most common cause of legal
blindness in the United States and
the leading cause of legal blindness in African-Americans.
It has
no symptoms at first. But over the years it can
steal your sight. With early treatment, you can
often protect your eyes against serious vision
problems.
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Risk
Factors for Glaucoma |
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Many
individuals are at a higher risk to develop glaucoma.
Following are the factors which increase the risk:
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Age:
Chronic glaucoma becomes much more common
with increasing age. It is uncommon below
the age of 40 but affects one percent of
people over this age and five percent over
65. |
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Race:
African Americans are at a higher risk of
developing chronic glaucoma than other racial
groups. |
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Family:
If you have a close relative who has chronic
glaucoma then you should have regular eye
examinations. You should advise other members
of your family to do the same. This is especially
true if you are over 40. |
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Near-sightedness:
People with a high degree of near-sightedness
are more prone to chronic glaucoma. |
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Systemic
Diseases: It is
believed that individuals with systemic
diseases such as diabetes, anemia, or hardening
of the arteries are at higher risk of developing
glaucoma. |
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Detection
of Glaucoma |
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Regular
eye exams by your ophthalmologist are the best
way to detect glaucoma. A glaucoma screening that
checks only the pressure of the eye is not sufficient
to determine if you have glaucoma. The only sure
way to detect glaucoma is to have a
complete eye exam. Your ophthalmologist
will perform the following tests:
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Visual
acuity: This eyez chart test
measures how well you see at various distances.
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Tonometry:
This standard test determines the
fluid pressure inside the eye using a tonometer.
A tonopen is a portable, hand-held instrument
that provides a safe, fast and accurate
method of testing intraocular pressure. |
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Gonioscopy:
Inspection of drainage
angle of your eye. |
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Ophthalmoscopy:
This examination provides your eye
doctor with a better view of the optic nerve
to check for signs of damage. To do this,
your eye care professional places drops
into the eye to dilate (widen) the pupil.
An ophthalmoscope is an instrument that
enables a doctor to examine the inside of
your eye. After the examination, your close-up
vision may remain blurred for several hours.
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Visual
Field (Perimetry): This test
measures your side (peripheral) vision.
It helps your eye doctor to find out if
you have lost side vision, a sign of glaucoma. |
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HRT:
This test analyzes the three-dimensional
structure of your optic nerve. |
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Pachymetry:
This test measures the thickness
of your cornea to evaluate the risk for
glaucoma. |
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Treatment
of Glaucoma |
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Treatment
for glaucoma consists of eye medication to lower
the pressure in the eye, laser treatment designed
to make the "drain" of the eye function
more efficiently, or surgery to create a new "drain"
in order to lower pressure. Many patients will
not have further loss of vision if the pressure
is lowered sufficiently.
Glaucoma can usually be treated effectively by
using eye drops or other medicines. In some cases
surgery may be necessary. Unfortunately, any loss
of vision from glaucoma cannot usually be restored.
But, early detection, prompt treatment and regular
monitoring can enable you to continue living in
much the same way as you have always lived. Protect
your eye health and your vision. Be sure to visit
our office regularly.
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Medicines:
Medicines are the most common early treatment
for glaucoma. They come in the form of eye drops
and pills. Some cause the eye to make less fluid.
Others lower pressure by helping fluid drain from
the eye. Glaucoma drugs may be taken several times
a day. Most people have no problems. However,
some medicines can cause headaches or have side
effects which affect other parts of the body.
Drops may cause stinging, burning, and redness
in the eye. Ask your eye doctor to show you how
to put the drops into your eye. In addition, tell
your ophthalmologist about other medications you
may be taking before you begin glaucoma treatment.
Many drugs are available to treat glaucoma. If
you have problems with one medication, tell your
ophthalmologist. Treatment using a different dosage
or a new drug may be possible. You will need to
use the drops and / or pills as long as they help
to control your eye pressure. This is very important.
Because glaucoma often has no symptoms, people
may be tempted to stop or may forget to take their
medicine. |
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Laser
Surgery: Laser surgery helps fluid
drain out of the eye. In open-angle glaucoma,
the drain itself is treated. The laser
is used to modify the drain (trabeculoplasty).
In angle-closure glaucoma, the laser creates
a hole in the iris (iridotomy) to improve
the flow of aqueous fluid to the drain.
Although your ophthalmologist may suggest
laser surgery at any time, it is often
done after trying treatment with medicines.
In many cases, you will need to keep taking
glaucoma drugs even after laser surgery.
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Laser surgery is performed in an ophthalmologist’s
office or eye clinic. Before the surgery,
your ophthalmologist will apply drops
to numb the eye. As you sit facing the
laser machine, your eye doctor
will hold a special lens to your eye.
A high-energy beam of light is aimed at
the lens and onto the meshwork
inside your eye. You may see flashes of
bright green or red light. The laser makes
50-100 evenly spaced burns. These burns
stretch the drainage holes in the meshwork.
This helps to open the holes and lets
fluid drain better through them.
Your ophthalmologist will check your eye
pressure shortly afterward. You will be
given some drops to take home for any
soreness or swelling inside the eye. You
will need to make several follow up visits
to have your pressure monitored. Once
you have had laser surgery over the entire
meshwork, further laser treatment may
not help. Studies show that laser surgery
is very good at getting the pressure down.
But its effects sometimes wear off over
time. Two years after laser surgery, the
pressure increases again in more than
half of all patients. |
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Conventional Surgery: The purpose of surgery is to make
a new opening for the fluid to leave the eye (trabeculectomy).
Although your ophthalmologist may suggest it at
any time, this surgery is often done after medicine
and laser surgery has failed to control your pressure.
Surgery is performed in a clinic or hospital. Before
the surgery, your eye surgeon gives you medicine
to help you relax and then small injections around
the eye to make it numb.
The surgeon then removes a small piece of tissue
from the white (sclera) of the eye. This creates
a new channel for fluid to drain from the eye. But
surgery does not leave an open hole in the eye.
The white of the eye is covered by a thin, clear
tissue called the conjunctiva. The fluid flows through
the new opening, under the conjunctiva, and drains
from the eye.
You must put drops in the eye for several weeks
after the operation to fight infection
and swelling. The drops will be different than the
eye drops you were using before surgery. You will
also need to make frequent visits to your eye doctor.
This is very important, especially in the first
few weeks after surgery.
In some patients, surgery is about 80 to 90 percent
effective at lowering pressure. However, if the
new drainage opening closes, a second operation
may be needed. Conventional surgery works best if
you have not had previous eye surgery, such as a
cataract
operation.
Keep in mind that while glaucoma surgery
may save remaining vision, it does not improve sight.
In fact, your vision may not be as good as it was
before surgery.
Like any operation, glaucoma surgery can cause side
effects. These include cataract, problems with the
cornea, inflammation or infection inside the eye,
and swelling of blood vessels behind the eye. However,
if you do have any of these problems, effective
treatments are available.
If you are concerned about glaucoma and would like
to schedule an eye appointment with NeoVision Eye
Center, please contact us at 510-431-5511
(Union City) or
650-962-4626 (Mountain
View). |
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